arch/x86/mm/hugetlbpage.c

   1 /*
   2  * IA-32 Huge TLB Page Support for Kernel.
   3  *
   4  * Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
   5  */
   6
   7 #include <linux/init.h>
   8 #include <linux/fs.h>
   9 #include <linux/mm.h>
  10 #include <linux/hugetlb.h>
  11 #include <linux/pagemap.h>
  12 #include <linux/slab.h>
  13 #include <linux/err.h>
  14 #include <linux/sysctl.h>
  15 #include <asm/mman.h>
  16 #include <asm/tlb.h>
  17 #include <asm/tlbflush.h>
  18
  19 static unsigned long page_table_shareable(struct vm_area_struct *svma,
  20                                 struct vm_area_struct *vma,
  21                                 unsigned long addr, pgoff_t idx)
  22 {
  23         unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) +
  24                                 svma->vm_start;
  25         unsigned long sbase = saddr & PUD_MASK;
  26         unsigned long s_end = sbase + PUD_SIZE;
  27
  28         /*
  29          * match the virtual addresses, permission and the alignment of the
  30          * page table page.
  31          */
  32         if (pmd_index(addr) != pmd_index(saddr) ||
  33             vma->vm_flags != svma->vm_flags ||
  34             sbase < svma->vm_start || svma->vm_end < s_end)
  35                 return 0;
  36
  37         return saddr;
  38 }
  39
  40 static int vma_shareable(struct vm_area_struct *vma, unsigned long addr)
  41 {
  42         unsigned long base = addr & PUD_MASK;
  43         unsigned long end = base + PUD_SIZE;
  44
  45         /*
  46          * check on proper vm_flags and page table alignment
  47          */
  48         if (vma->vm_flags & VM_MAYSHARE &&
  49             vma->vm_start <= base && end <= vma->vm_end)
  50                 return 1;
  51         return 0;
  52 }
  53
  54 /*
  55  * search for a shareable pmd page for hugetlb.
  56  */
  57 static void huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
  58 {
  59         struct vm_area_struct *vma = find_vma(mm, addr);
  60         struct address_space *mapping = vma->vm_file->f_mapping;
  61         pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
  62                         vma->vm_pgoff;
  63         struct prio_tree_iter iter;
  64         struct vm_area_struct *svma;
  65         unsigned long saddr;
  66         pte_t *spte = NULL;
  67
  68         if (!vma_shareable(vma, addr))
  69                 return;
  70
  71         spin_lock(&mapping->i_mmap_lock);
  72         vma_prio_tree_foreach(svma, &iter, &mapping->i_mmap, idx, idx) {
  73                 if (svma == vma)
  74                         continue;
  75
  76                 saddr = page_table_shareable(svma, vma, addr, idx);
  77                 if (saddr) {
  78                         spte = huge_pte_offset(svma->vm_mm, saddr);
  79                         if (spte) {
  80                                 get_page(virt_to_page(spte));
  81                                 break;
  82                         }
  83                 }
  84         }
  85
  86         if (!spte)
  87                 goto out;
  88
  89         spin_lock(&mm->page_table_lock);
  90         if (pud_none(*pud))
  91                 pud_populate(mm, pud, (unsigned long) spte & PAGE_MASK);
  92         else
  93                 put_page(virt_to_page(spte));
  94         spin_unlock(&mm->page_table_lock);
  95 out:
  96         spin_unlock(&mapping->i_mmap_lock);
  97 }
  98
  99 /*
 100  * unmap huge page backed by shared pte.
 101  *
 102  * Hugetlb pte page is ref counted at the time of mapping.  If pte is shared
 103  * indicated by page_count > 1, unmap is achieved by clearing pud and
 104  * decrementing the ref count. If count == 1, the pte page is not shared.
 105  *
 106  * called with vma->vm_mm->page_table_lock held.
 107  *
 108  * returns: 1 successfully unmapped a shared pte page
 109  *          0 the underlying pte page is not shared, or it is the last user
 110  */
 111 int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
 112 {
 113         pgd_t *pgd = pgd_offset(mm, *addr);
 114         pud_t *pud = pud_offset(pgd, *addr);
 115
 116         BUG_ON(page_count(virt_to_page(ptep)) == 0);
 117         if (page_count(virt_to_page(ptep)) == 1)
 118                 return 0;
 119
 120         pud_clear(pud);
 121         put_page(virt_to_page(ptep));
 122         *addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE;
 123         return 1;
 124 }
 125
 126 pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr)
 127 {
 128         pgd_t *pgd;
 129         pud_t *pud;
 130         pte_t *pte = NULL;
 131
 132         pgd = pgd_offset(mm, addr);
 133         pud = pud_alloc(mm, pgd, addr);
 134         if (pud) {
 135                 if (pud_none(*pud))
 136                         huge_pmd_share(mm, addr, pud);
 137                 pte = (pte_t *) pmd_alloc(mm, pud, addr);
 138         }
 139         BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte));
 140
 141         return pte;
 142 }
 143
 144 pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
 145 {
 146         pgd_t *pgd;
 147         pud_t *pud;
 148         pmd_t *pmd = NULL;
 149
 150         pgd = pgd_offset(mm, addr);
 151         if (pgd_present(*pgd)) {
 152                 pud = pud_offset(pgd, addr);
 153                 if (pud_present(*pud))
 154                         pmd = pmd_offset(pud, addr);
 155         }
 156         return (pte_t *) pmd;
 157 }
 158
 159 #if 0   /* This is just for testing */
 160 struct page *
 161 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 162 {
 163         unsigned long start = address;
 164         int length = 1;
 165         int nr;
 166         struct page *page;
 167         struct vm_area_struct *vma;
 168
 169         vma = find_vma(mm, addr);
 170         if (!vma || !is_vm_hugetlb_page(vma))
 171                 return ERR_PTR(-EINVAL);
 172
 173         pte = huge_pte_offset(mm, address);
 174
 175         /* hugetlb should be locked, and hence, prefaulted */
 176         WARN_ON(!pte || pte_none(*pte));
 177
 178         page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
 179
 180         WARN_ON(!PageCompound(page));
 181
 182         return page;
 183 }
 184
 185 int pmd_huge(pmd_t pmd)
 186 {
 187         return 0;
 188 }
 189
 190 struct page *
 191 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 192                 pmd_t *pmd, int write)
 193 {
 194         return NULL;
 195 }
 196
 197 #else
 198
 199 struct page *
 200 follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 201 {
 202         return ERR_PTR(-EINVAL);
 203 }
 204
 205 int pmd_huge(pmd_t pmd)
 206 {
 207         return !!(pmd_val(pmd) & _PAGE_PSE);
 208 }
 209
 210 struct page *
 211 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 212                 pmd_t *pmd, int write)
 213 {
 214         struct page *page;
 215
 216         page = pte_page(*(pte_t *)pmd);
 217         if (page)
 218                 page += ((address & ~HPAGE_MASK) >> PAGE_SHIFT);
 219         return page;
 220 }
 221 #endif
 222
 223 /* x86_64 also uses this file */
 224
 225 #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
 226 static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
 227                 unsigned long addr, unsigned long len,
 228                 unsigned long pgoff, unsigned long flags)
 229 {
 230         struct mm_struct *mm = current->mm;
 231         struct vm_area_struct *vma;
 232         unsigned long start_addr;
 233
 234         if (len > mm->cached_hole_size) {
 235                 start_addr = mm->free_area_cache;
 236         } else {
 237                 start_addr = TASK_UNMAPPED_BASE;
 238                 mm->cached_hole_size = 0;
 239         }
 240
 241 full_search:
 242         addr = ALIGN(start_addr, HPAGE_SIZE);
 243
 244         for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
 245                 /* At this point:  (!vma || addr < vma->vm_end). */
 246                 if (TASK_SIZE - len < addr) {
 247                         /*
 248                          * Start a new search - just in case we missed
 249                          * some holes.
 250                          */
 251                         if (start_addr != TASK_UNMAPPED_BASE) {
 252                                 start_addr = TASK_UNMAPPED_BASE;
 253                                 mm->cached_hole_size = 0;
 254                                 goto full_search;
 255                         }
 256                         return -ENOMEM;
 257                 }
 258                 if (!vma || addr + len <= vma->vm_start) {
 259                         mm->free_area_cache = addr + len;
 260                         return addr;
 261                 }
 262                 if (addr + mm->cached_hole_size < vma->vm_start)
 263                         mm->cached_hole_size = vma->vm_start - addr;
 264                 addr = ALIGN(vma->vm_end, HPAGE_SIZE);
 265         }
 266 }
 267
 268 static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
 269                 unsigned long addr0, unsigned long len,
 270                 unsigned long pgoff, unsigned long flags)
 271 {
 272         struct mm_struct *mm = current->mm;
 273         struct vm_area_struct *vma, *prev_vma;
 274         unsigned long base = mm->mmap_base, addr = addr0;
 275         unsigned long largest_hole = mm->cached_hole_size;
 276         int first_time = 1;
 277
 278         /* don't allow allocations above current base */
 279         if (mm->free_area_cache > base)
 280                 mm->free_area_cache = base;
 281
 282         if (len <= largest_hole) {
 283                 largest_hole = 0;
 284                 mm->free_area_cache  = base;
 285         }
 286 try_again:
 287         /* make sure it can fit in the remaining address space */
 288         if (mm->free_area_cache < len)
 289                 goto fail;
 290
 291         /* either no address requested or cant fit in requested address hole */
 292         addr = (mm->free_area_cache - len) & HPAGE_MASK;
 293         do {
 294                 /*
 295                  * Lookup failure means no vma is above this address,
 296                  * i.e. return with success:
 297                  */
 298                 if (!(vma = find_vma_prev(mm, addr, &prev_vma)))
 299                         return addr;
 300
 301                 /*
 302                  * new region fits between prev_vma->vm_end and
 303                  * vma->vm_start, use it:
 304                  */
 305                 if (addr + len <= vma->vm_start &&
 306                             (!prev_vma || (addr >= prev_vma->vm_end))) {
 307                         /* remember the address as a hint for next time */
 308                         mm->cached_hole_size = largest_hole;
 309                         return (mm->free_area_cache = addr);
 310                 } else {
 311                         /* pull free_area_cache down to the first hole */
 312                         if (mm->free_area_cache == vma->vm_end) {
 313                                 mm->free_area_cache = vma->vm_start;
 314                                 mm->cached_hole_size = largest_hole;
 315                         }
 316                 }
 317
 318                 /* remember the largest hole we saw so far */
 319                 if (addr + largest_hole < vma->vm_start)
 320                         largest_hole = vma->vm_start - addr;
 321
 322                 /* try just below the current vma->vm_start */
 323                 addr = (vma->vm_start - len) & HPAGE_MASK;
 324         } while (len <= vma->vm_start);
 325
 326 fail:
 327         /*
 328          * if hint left us with no space for the requested
 329          * mapping then try again:
 330          */
 331         if (first_time) {
 332                 mm->free_area_cache = base;
 333                 largest_hole = 0;
 334                 first_time = 0;
 335                 goto try_again;
 336         }
 337         /*
 338          * A failed mmap() very likely causes application failure,
 339          * so fall back to the bottom-up function here. This scenario
 340          * can happen with large stack limits and large mmap()
 341          * allocations.
 342          */
 343         mm->free_area_cache = TASK_UNMAPPED_BASE;
 344         mm->cached_hole_size = ~0UL;
 345         addr = hugetlb_get_unmapped_area_bottomup(file, addr0,
 346                         len, pgoff, flags);
 347
 348         /*
 349          * Restore the topdown base:
 350          */
 351         mm->free_area_cache = base;
 352         mm->cached_hole_size = ~0UL;
 353
 354         return addr;
 355 }
 356
 357 unsigned long
 358 hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 359                 unsigned long len, unsigned long pgoff, unsigned long flags)
 360 {
 361         struct mm_struct *mm = current->mm;
 362         struct vm_area_struct *vma;
 363
 364         if (len & ~HPAGE_MASK)
 365                 return -EINVAL;
 366         if (len > TASK_SIZE)
 367                 return -ENOMEM;
 368
 369         if (flags & MAP_FIXED) {
 370                 if (prepare_hugepage_range(addr, len))
 371                         return -EINVAL;
 372                 return addr;
 373         }
 374
 375         if (addr) {
 376                 addr = ALIGN(addr, HPAGE_SIZE);
 377                 vma = find_vma(mm, addr);
 378                 if (TASK_SIZE - len >= addr &&
 379                     (!vma || addr + len <= vma->vm_start))
 380                         return addr;
 381         }
 382         if (mm->get_unmapped_area == arch_get_unmapped_area)
 383                 return hugetlb_get_unmapped_area_bottomup(file, addr, len,
 384                                 pgoff, flags);
 385         else
 386                 return hugetlb_get_unmapped_area_topdown(file, addr, len,
 387                                 pgoff, flags);
 388 }
 389
 390 #endif /*HAVE_ARCH_HUGETLB_UNMAPPED_AREA*/
 391